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Climate, culture linked in prehistoric Northeast

By Carolyn Y. Johnson
Globe Staff / December 20, 2010

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Though climate change seems a particularly modern predicament — one that generates alarm about the fate of the planet and how people and businesses will adapt — scientists are finding evidence that climate fluctuations influenced cultural changes among inhabitants of prehistoric New England.

Research is revealing the interconnected relationship between environmental shifts and changes in prehistoric people’s tools and settlement patterns. At the end of a cold period came the end of a particular type of chipped stone point used in hunting; when surface water temperatures cooled, burial traditions shifted.

“It’s a reminder that climate has changed in the past, but it’s also a reminder that cultures either have to change or get changed, whether they like it or not, when the climate changes,’’ said Arthur Spiess, senior archeologist at the Maine Historic Preservation Commission.

Archeologists have long debated how environmental changes shaped the lives of people. Today, big sets of data are allowing them to look more closely at possible correlations between human and ecological changes in prehistory. Research published this month found that every time the climatic needle jumped in the Northeast, so did human culture. That work builds on a 2005 study that looked closely at a 1,300-year mini ice age followed by rapid warming, and the simultaneous abrupt change in both the landscape and hunting tools.

“If you persistently see these time-synchronous changes, it certainly says that climate change is playing a role in why people are changing the tool types and materials they use,’’ said Paige Newby, a postdoctoral researcher in geological sciences at Brown University who worked with Spiess on the 2005 paper published in the journal Quaternary Science Reviews.

The findings suggest culture has changed with the climate, but they do not necessarily predict what will happen in the future, since hunter-gatherers would have been sensitive to environmental shifts in a way that people today are not.

Because the remnants of prehistoric people’s lives are fragmentary, archeologists use what they can to draw inferences. In the new work, published in the Proceedings of the National Academy of Sciences, researchers drew on a database of nearly 1,900 prehistoric remnants from Pennsylvania to Maine that were analyzed with radiocarbon dating. They also used pollen and charcoal records to understand shifts in vegetation and to estimate the size of the human population.

Led by Samuel Munoz, now a graduate student at the University of Wisconsin Madison, researchers found that climate and human changes seemed to happen in step. Paleo-Indians, hunter-gatherers known for elegant fluted arrowheads chipped from stone, lived in the region from about 13,500 to 11,250 years ago, when the area had a tundra-like landscape with spruce and sedges. They may have hunted caribou.

But around 11,600 years ago, the climate warmed rapidly, and pine forests encroached. At the same time, the archeological records shift to a different culture — that of the Archaic period, with people who were less nomadic and hunted smaller game using a different style of pointed stone. They are also thought to have started fishing.

Researchers did not examine exactly how or why such changes occurred, but Newby’s work suggests that as the landscape changed, people may have begun hunting solitary animals in forests rather than herds of caribou, with different hunting tools.

Spiess, who was not involved in the new research, noted that about 3,800 years ago, when surface water temperatures cooled in the Gulf of Maine, another transition occurred: from people who buried their dead with functional stone artifacts, to a different culture — possibly outsiders — who cremated their dead.

“Where life gets tough for a group of people, that allows another group of people to expand,’’ Spiess said.

About 3,000 years ago, when there was a change in lake levels, the Woodland culture emerged, whose people used pottery and began to cultivate plants.

Researchers are careful to say it is not simple cause and effect, with climate changes directly altering human life. But coincident changes in people and the environment should be studied to understand the causes, they say. And artifacts that have been dug up may be signs of broader shifts.

“It’s not a straightforward relationship,’’ Munoz said. “Pottery is probably symbolic of change in general, but it is what gets preserved and what’s most obvious and indicative.’’

Brian Robinson, an archeologist at the University of Maine, said there is no doubt climate change can affect lifestyles. But he pointed out that environmental change would not have been uniform across such a large area, and that the radiocarbon dates are a “shaky’’ signature of population and cultural change, in part because the database does not include enough details about how archeologists decided which culture each artifact is from.

Newby and colleagues are seeking funding for a study to examine the span between 10,000 to 12,000 years ago for evidence of environmental changes leaving an imprint on culture. It’s a period of particular interest, said Richard Boisvert, New Hampshire’s state archeologist, and scientists can now use ice core data and sediment cores to understand what happened.

“Do we really see specific changes marching in step with environmental changes?’’ Boisvert asked. “We think the answer is yes. But what are these changes, and can we guess why?’’

Carolyn Y. Johnson can be reached at cjohnson@globe.com.

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